Wednesday, August 21, 2013

A common denizen of forested areas with rich, moist soil, the gracefully arching fronds of the Ostrich Fern typically grow in circular groups. Since this showy fern makes a desirable subject for shady areas of gardens it's easy to find some growing closer to home, for example, along the front porch of the Tweed Heritage Center.

The distinctive sterile fronds – these examples are about one meter in length – are widest close to their tops and thereafter briskly taper toward their tips.

The fertile fronds in mid-August.

Mature fertile fronds in mid-September.

A closer look at the lobed sterile pinnae; note that the veins extend to the margins and are not forked.

The stipe is deeply grooved toward its base, with the small pinnae near the bottom of the frond tending to clasp the stipe.

The adult Cecropia Moth has a less gaudy but still beautiful color scheme. And ironically, although the caterpillar eats, and eats, and eats, the adult moth doesn't, it exists only to find a mate and lay eggs, and after a week to ten days ... it dies ...

Tuesday, August 13, 2013

The strange and weird things one learns from the most mundane circumstances.

The green growths on a stone fished out of the Moira River are colonies of – I'm still not entirely clear which – either a blue-green cyanobacterium called Nostoc parmelioides, or an algae composed of the bacteria.

This organism is symbiotic with a tiny species of midge called Cricotopus nostocicola, the larvae of which develop in the algae, changing its form from small round growths to a semi-circular shapes; both versions can be seen in this picture. The Cricotopus larvae are supposed to be visible within the semi-circular colonies – how large are they, and is my camera's macro good enough to capture an image?

Ancient ancestors of cyanobacteria oxygenated our planet's atmosphere about 2½ billion years ago. Prior to the "Great Oxidization Event" Earth's early atmosphere was believed to consist of gases much like Saturn's moon Titan, hardly conducive for life on Earth as we know it today. The oxygen in the atmosphere also combined with the extant minerals to form new mineral species.

Some cyanobacteria play a role in nitrogen fixation, some are symbionts in lichens, they live in the fur of sloths, and on the negative side they can cause toxic algal blooms. It isn't stretching the truth to say that cyanobacteria were a major force in the shaping of this planet and the life upon it – we literally wouldn't be here without them – and they continue to play significant roles in the tangled webs of its ecosystems.

Re-visting the river a couple of days later in the hopes of finding some Cricotopus larvae, or whatever midge larvae are called ... midge maggots?

Blue-green algae or cyanobacteria ... other than that I have no idea what this stuff is, or even if it's all the same species. Sometimes it's found growing in tangled masses of filaments, or it may be organized in lacy branches.

Still hard at work after billions of years ... the bubbles trapped within this mass of blue-green algae are presumably oxygen. There was also evidence of lots of decayed algae, the decomposition process presumably using up the some of the aforementioned oxygen. Increased amounts of nutrients such as phosphates can cause the cycle of phytoplankton growth and decay to spiral out of control, initiating a process know as hypertrophication.

Getting back to the Nostoc parmelioides cyanobacteria and their Cricotopus spp. insect partners – I removed and examined some of the bracket-shaped growths and the midge larvae are naked-eye visible within the algae. The insect is coiled in a spiral with its head near the center of the circled area. The roughly circular shapes are about 5 to 6 mm across, and the larvae fully stretched out are 3 mm long at the most.

I also dissected a couple of the growths and managed to acquire some half decent macros of the Cricotopus larvae. It's no mean feat to peel the algae apart without damaging or killing the tiny insects using a jack-knife as a dissecting tool.

While studying and photographing the algae it was impossible to miss the uncountable numbers of what appeared to be very small, perhaps 4 mm long, caddis fly casings attached to the rocks at the bottom of the river. The closest match at BugGuide.Net is Brachycentrus appalachia, but it's pushing it to identify these diminutive insects to the species level based on the paucity of detail visible in the pictures.

All this "R&R" – research and reading – because I paused for a moment to indulge my curiosity and photographed some "scum" sprouting on a rock in the river ...

This isn't the kind of photography everyone might appreciate, but it's the reality of the world of nature. Predation and parasitism are an integral part of the story of life and have been going on for millions of years, nor are we exempt from the cycle.

I've never seen anything like this! I've heard of large Bullfrogs eating small snakes and have seen them dispatch smaller frogs, including cannibalizing their own kind, but this is the only instance I've observed one eating a bird.

The fledgling flew into – or too close – to the water, and the Bullfrog had caught it headfirst and was sculling backwards with its webbed feet, dragging the bird underwater and drowning it like a crocodile would an antelope. And this wasn't a particularly large frog, only about four inches long.

Pushing with its front feet the frog eventually managed to force its victim half-way down its gullet, but couldn't "swallow" its prey and eventually disgorged it.

It's a good thing these distant cousins of frogs are extinct, because WE wouldn't be safe walking along the shore. Judging by the number of fossils Eryops megacephalus ("megacephalus" means big or large head) was a successful predator and quite common in its time. Of course there are still crocodiles, hippos, mosquitos, etc ... not to mention a top predator that has been responsible for more deaths than any other species ...

Stream Bluet (Enallagma exsulans), female – this specimen was so aberrantly marked and colored compared to the norm for this area that I mistook it for a female Double-striped Bluet. The postocular spots are very small, the paler stripes within the middorsal carina and humeral stripe are quite pronounced, and the "W" on S9 is relatively elongated.

The lines on the middorsal carina and humeral stripes of local female Stream Bluets I've encountered in the past few years are barely visible. And the "W"-shaped spots on their ninth abdominal segments generally look exactly like a "W"; the next two images illustrate a couple of variations.

However, were this a Double-striped Bluet it would be hundreds of kilometers from home. Not impossible, as I recently found a group of Slender Bluets breeding in Stoco Lake. But the habitat is also be wrong – I found this damselfly along the Moira River where the water runs fast and the bottom is rocky, ideal Stream Bluet territory. Double-striped Bluets prefer ponds and lakes, or the slower portions of streams and rivers. And having researched images of other female Stream Bluets on the Internet and obtained some second opinions (at BugGuide.Net) the conclusion is – yes, this is indeed a Stream Bluet.

Alhough it would have been exciting to have stumbled upon another odonate species outside of its historical range, I would never in any event accept this as a Double-striped Bluet sighting without checking the mesostigmal plates or seeing and/or photographing a male or a mating pair.

Friday, August 9, 2013

Found buried in a sand-bottomed stream flowing through a wooded area, 25 mm in length, it's definitely Cordulegaster spp. – but which one?

There are three members the family Cordulegastridae in our area: the Delta-spotted Spiketail (Cordulegaster diastatops), the Twin-spotted Spiketail (Cordulegaster maculata), and the Arrowhead Spiketail (Cordulegaster obliqua). According to the Ontario Odonata Summary Atlas the Arrowhead Spiketail is by all accounts an uncommon dragonfly and it's tempting to rule it out on this basis. But by the same token the naiad was encountered in appropriate habitat within half a kilometer of where an adult female Cordulegaster obliqua was sighted and photographed in mid-June of 2011.

The next picture was taken indoors using the flash ... not much of an improvement, but a friend with a better camera has taken some cleaner, more detailed images under brighter lighting. The photos in this post have been submitted to BugGuide.Net, and maybe someone who has experience with identifying odonate naiads can take this to the species level. (EDIT ... one of the forum members has posted a Key to the Michigan Species of Cordulegaster, and it doesn't look like these images are going to be good enough ...)

The youngster ate two mosquito larvae while in captivity, and upon being returned to the stream where it was found it quickly proceeded to bury itself in the sand and silt. Spiketail larvae hunt by concealing themselves under the sediment and leaving only their eyes exposed, lurking in ambush for an unwary passerby. Hopefully it will survive the hurdles of larval life long enough to attain maturity, and who knows, we may meet again and it can pose for more photos next summer ...

Where there's one Spiketail naiad it's reasonable to expect there might be others, so it looks like more forays to the woodland stream in the near future to acquire a larger, older instar to study.

The story continues ... upon visting a stretch of the woodland stream between the trans-Canada Trail and Lakeview Lane, a little south of the site of yesterday's find, I discovered that it's virtually crawling with Spiketail larvae! Within a distance of no more than three meters I found four naiads between 15 and 18 mm in length, one the same size as the previous day's find (25 mm), and four at 35 mm. (I should have saved all of the naiads and done a group shot.)

If they survive that long, three of these will emerge and transform into adults next year, and one, the first of today's finds, will not, as it was dead when I came upon it. Bad luck for the naiad, but this gave me an opportunity to photograph the prementum and palps on a relatively large specimen. Here are the images in the order they were acquired, and it's only fair to point out that this isn't really good science, as the characteristics we're looking at in the following images are not attributes of the same individual.

The best available macros of the outer surface of the serrated palps, the palpal setae and the premental setae. There are six palpal setae – although only five hairs are visible in the image there are six "roots" and the other palp has six as well (not visible due to the angle the photo). There appear to be ten, not more than eleven, premental setae. Unfortunately, being new to this, I neglected to acquire an image of the epaulet.

One of the smaller – 15 to 18 mm – naiads.

Another large (35 mm) – but alive – individual. Since I didn't have a ruler to determine the length of the insects I used a stick or my spare key, which were measured after I went home.

The frontal shelf (the part of the head between the antennae) is rounded in dorsal view. Another error in judgement due to inexperience ... while in the field I never thought to photograph or at least examine the frontal shelf's lateral aspect on any of the naiads.

A ventral view ... scaling the prementum as best I can on the computer screen, the palpal width is at least 2.5× the basal width.

A couple of views of the abdomen. The lateral spine of S8 does not appear to be strongly upcurved, in fact, I can't really see any lateral spines, just hair ....

The Spiketail naiad in its habitat upon being released, out of focus since it's both underwater and in motion. Being submerged brings forth a lot subtle, beautiful colors that completely disappear when the insects are removed from their natural element.

Knowing the length of a female naiad's developing ovipositor in relation to S9 would be helpful, but all of the specimens examined today, save the naiad in the next collection of images, were either too young to have developed an ovipositor or were males. This individual was also 35 mm in length and doesn't appear any different from the other naiads examined thus far ... except ... look carefully at the lateral views of the abdomen.

There's no evidence of an upcurved lateral spine on S8.

Jackpot! This one's a girl and the ovipositor is clearly a little longer than S9.

A few pictures of the larva after it was set free to go on its way, again, there's a striking difference in appearance compared to when it was perching on the palm of my hand. As with the other naiads captured, I didn't take any photos of the mouth parts and associated setae, as I didn't feel I could accomplish this without injuring the insects.

Assuming the naiads are all the same species and share all of the above characteristics (no, this definitely isn't exemplary science), and looking at that Key to the Michigan Species of Cordulegaster, it's safe to rule out the Delta-spotted Spiketail (Cordulegaster diastatops). There do appear to be six palpal setae, or the roots thereof if not the actual setae, but I do not count more than eleven premental setae. And – the ovipositor of the female is definitely longer than S9.

So it's still a bit of an open question because of inconsistencies in the number of palpal setae, but for now the weight of the evidence points toward the Twin-spotted Spiketail (Cordulegaster maculata). Despite the numbers of larvae, and although this species does range in this area, I have never encounterd it in its adult incarnation. But next summer I will certainly be staking out this stream when the Twin-spotted Spiketails are expected to emerge and fly in early June.

August 12th ... checking out a section of the stream to the north of the trans-Canada Trail turned up half a dozen naiads. Four larvae were between 15 and 20 mm in length, and another two larger specimens measured 30 to 35 mm long. This makes for a grand total of sixteen in a fairly short stretch of water, so the Spiketails are hardly uncommon. Yet I have only encountered one adult in five years!?